Cycles Dough Material - Transpanrency as function of strechting

Dear all,

for an animation i need a dough - of cloth - material, that changes its transparency depending on how much the body that uses the material is stretched, like shown in this picture:


What i mean is that ia have on object, e.g. a soft body, an when i strech it, it will become more transparent in its streched areas. Is this a job for SSS? I tried the sss node on a soft body that has been streched, but the surface transparency remain the same.

I hope some one could help me.

Thanks in advance an Greetings from Germany,

Andreas

SSS itself is opaque, so it would have to be mixed with a transparent node in some way. perhaps?:


(slight tweak to BlenderDipolm’s ‘tutorial: absorption in cycles’)

edit: After some messing around with this, it doesn’t really work…

Projecting a UV map down through it, and using the red channel -> ramp as height seems to work as a factor between the SSS & Transparent, but the raylength thing absolutely doesn’t…

You don’t want transparency, you want translucency. SSS will do that to some extent, maybe enough, but you might want to mix translucent with it.

The easiest way to do it would be to download a newer trunk build with volume rendering and simulate the effect using a real scattering volume. A trickier way might be to mix a glass shader with the SSS shader according to data obtained from the ‘ray length’ output of the light-path node, which I found from an initial test might actually work.

But maybe i’m not understanding the problem…

If your animation is such that your object stretches and becomes thin in some places it’s the same as a static object that is thick in some places and thin in others so I quickly did such an object, threw the shader mix on it and put it in front of a light source as you have in your example…


I really don’t know if translucency will work because the reference image actually shows that when the dough is thin enough, you can literally see through it (this type of thing needs to be done with a glass shader or refractive shader with the roughness value set to 1 because you can’t change the way the light scatters in the translucent node).

Ah, OK I didn’t see that in the reference… still don’t, except for the holes… translucence is quite good at picking up the shadows cast on the other side of a thin object and I thought that’s what I was looking at.

The only reason I even mixed in the SSS node is that translucence doesn’t have good resolution for finer detail - it simulates too much scatter and not enough absorption…

I mean they’re both economical alternatives to true volume, right?